Is a TriangleTube Prestige Trimax Excellence PTE 110 the right one of the job?

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Dana

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Reason that I brought up air-sealing and insulation is that several heating contractors are concerned that the
TT prestige trimax series 60 (input modulation of 16 to 60K MBH) would not be able to supply enough heat for the whole house.

And unless they did a careful fuel-use analysis on the previous system and an honest Manual-J or even an I=B=R spreadsheet calc, their opinions aren't worth the toilet-paper they wrote it on. Fear of undersizing is rampant amongst hacks, but rarely justifiable. The more reasonable fear should be of oversizing.

Air sealing is almost always cost-effective, as is fixing any gaps in the insulation, and those measures DO lower the heat load. But the notion that an 1800' house in Westchester needs more than 55,000BTU/hr of boiler output (that's 30 BTU/ft-hr!) is just nuts, unless there is literally no insulation in the walls, and all of the windows are single-pane, all of which would be necessary & cost-effective things to rectify on comfort grounds alone. Ratio rules of thumb are pretty lousy gauges of reality, but most 1920s homes won't run more than ~20 BTU/ft-hr , and will often be in the 15BTU/ft-hr range with a bit of air sealing and (usually absent) foundation insulation. At the more likely 20 BTU/ft-hr an 1800' house would only need 36,000 BTU/hr which is barely over the MINIMUM output of the -110.

As-zoned the -110 is guaranteed to short-cycle at condensing temps- you'd literally be better off with ~100KBTU/hr mid-efficiency cast iron boiler with smarter controls if you're hell-bent on installing a boiler that oversized. You only get the benefits of mod-con efficiency if it's actually modulating and condensing, which is why you HAVE to install the smallest one that actually meets the load, and have small zones of low-mass-low-emittance radiation like fin-tube.

Run a crude I=B=R spreadsheet on your house on a room-by-room basis. Assume an interior temp of 70F, exterior 12F for a 58F delta. For any double pane windows of unknown U-factor or any single-pane + storm, and exterior doors use 0.5 BTU/degree-ft. For all 2x4 framed wall area with at least some type of insulation use 0.1 BTU/degree-ft, for any 2x6 use 0.08. For an attic with anything better than sloppily installed R19s use 0.07. For uninsulated above-grade foundation down to a foot below grade, use 1BTU/degree-foot.

A typical 1800' house will have about 270' of window, and assuming a couple of exterior doors, call it 40' of door for 310 square feet of window + door:

U0.5 x 310' x 58F= 8990 BTU/hr

A typical 1800' 2-story will have 900' of attic floor:

U0.07 x 900' x 58F= 3654 BTU/hr

Assuming a perimeter of say 180' and 2' of above/near grade foundation for 360' of U 1.0), and a basement 15F colder than the upstairs when it's +12 F outside you're looking at.

U 1 x 360 x 43F= 15,480 BTU/hr

Assuming 10' per story and 180' of perimeter you have 1800' of gross wall area, less 310' of window & door leaves 1490' of U0.1:

U0.1 x 1490 x 58F= 8642 BTU/hr.

For 900' of U 0.07 attic you get:

U0.07 x 900' x 58F= 3654 BTU/hr.

Add it all up and you're at 40,420 BTU/hr. Add 30% 'cuz you live in the absolute DRAFTIEST house in Westchester (or always sleep with the windows open, even when it's +12 F outside) and you're still only at 52,546 BTU/hr, a load still covered by the -60 running with 160F output.

And those U-factors presume some pretty crummy & poorly installed insulation- reality is almost always better than that (or could be made better than that at very low cost). You'll note the biggest single number is usually an uninsulated unheated basement, which is an upgrade needed by more than half the homes in Westchester county NY. It's not super-cheap to retrofit foundation insulation, but there are lower cost and higher cost ways to get there. Using even intermediate-cost methods (say, 2" of closed cell spray foam + intumescent paint, at ~$3 per square foot) it's worth it, even at buck-a-therm gas.

Seriously- take the time to measure up your house on a room by room basis and use a spreadsheet tool to come up with the numbers- they're a lot lower than your bidding contractors think. Buy some low-E storms to retrofit on those colder rooms, or install more radiation in those rooms, and buy some air-sealing & insulation if you think it's still too drafty.
 

Jadnashua

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The last thing a contractor wants is to put in a new system and then you tell them it can't keep the house warm. So, the easy thing is to put on one bigger than needed. It also gets them more money, since the bigger it is, the more it costs. But, if you want it done right, you have to be smarter, especially if you want to maximize your investment. Contractors don't like to argue with people when they are taking out a 150K BTU unit, and replacing it with a 60K unit, people just assume they need the same size as what was there originally. Well, energy costs are way higher now, and the technology is better...you really NEED to match your load with the properly sized supply.

What people here have been trying to tell you is that those contractors are taking the easy way out, and it will NOT end up in saving you money. WHen it comes to things like heating appliances, they work much more efficiently when they run long burns. That can ONLY happen when it is sized properly. On/off cycles kill efficiency and can hurt longevity...things work better, longer, when they don't turn on/off a lot. A boiler that is too big will need to turn on/off LOTS!

If you take a weird situation where you have the coldest week in 100-years and your system was typically just able to keep up normally, the house might cool off a degree or two - it won't immediately (or ever!) turn into a refrigerator! It might take longer to reheat if you turned the heat way down while on vacation, but then, again, only on that really cold day...you're somewhat limited by the radiators in the house, they can only output so much heat, regardless of what type of supply you have.
 

Dana

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Thing is, his real heat load probably IS no more than about 36-40K, even as-is, with no building improvements, which means even with the -60 he would be good down well into negative double digit temps from a boiler output point of view. The hacks recommending the bigger boilers are just that, hacks.

Anybody who has bothered to work through more than a couple of real heat load calcs would be able to tell you that at a 99% outside design temp 30BTU/foot is an insane number for an 1800' house that has glass in the windows, and doors that shut. Move the same house to Fairbanks and sure, it could be 30BTU/ft. But that is STILL a heat load that could be delivered by the -60(!).

So why would anybody even consider installing a -110 in that house?

Ignorance & apathy would be my best guess, but there could be other reasons I s'pose.

But if they're not even willing to do a heat load calc it leaves me wondering what other critical system design aspects they're missing? They clearly missed the boat on the short fin-tube zone short-cycling problem, and that's dead obvious even on the napkin-math model. (Any real mod-con system designer/installer would have flagged that as a high-potential problem for the -110 without even breaking out the crayons.)
 

BadgerBoilerMN

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Before we install buffer tanks (generally expensive, if properly sized, installed and controlled) we try to specify more radiation in the form of sub-floor radiation, radiant ceilings or real wall-hung panel radiators sized for low temperature. This is a long-term investment in comfort and economy.

Sizing a micro-zone may be as simple as tying it to another (not letting it call the boiler) or knowing from your room-by-room heat load analysis, that the micro-zone will never, or rarely, call by itself.

All residential high efficiency condensing boilers modulate flame and feature on-board outdoor reset.

Buffer tanks must be sized by an experienced designer, no WAGS will work.
 

Dana

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As previously discussed, even if he tied his 30' & 34' sticks of fin tube together operating in condensing mode would be a serious problem for the -110, but you might be able to deal with it on the -60. As separate zones they'll still be problematic even with the -60.

CLEARLY this system needs a real designer, not a hack-installer to run it on a mod-con. If he's leaving the zones alone and there's a dearth of design talent available, a tiniest in class 2-3 plate mid-efficiency cast iron boiler with heat-purge controls would come pretty close to hitting it's AFUE numbers, leaving some cash on the table to spend on the building envelope to reduce the load in his colder zones. If this place has no foundation insulation and leaks a lot of air, fixing those issues + tiny cast iron are probably more cost effective than adding sufficient radiation (or mass) to deal with a mod-con.

I wonder what fraction of already-installed mod-con boilers are as ridiculously oversized for their loads as the -110 would be for this one? (I'm guessing it's more than 30%, maybe even 50%, based solely on how common threads like this are.)
 

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What companies are selling 2-3 plate mid-efficiency cast iron boilers?

Regards,

AlexanderNY
 

Dana

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Lots of 'em.

The smallest Burnham ES2 might be a good prospect, only ~1.5-2x oversized for the likely load, plenty of smart-control options for both comfort & efficiency. Less than $2K for the hardware @ internet pricing. It tolerates 110F return water without exterior plumbing, and has hooks for quickly integrating outdoor reset with an add-on card. Even a hack of an installer should be able to handle it, and would have to get creative to really screw it up.

The smallest Buderus GC124 or GA124 would be in that class, but usually for more money. The GA124 is designed with smart controls in mind, the GC not so much.

The smallest Biasi B10 , the B-3 is a 3 plate boiler, but retrofit heat purge controls would be necessary to get the most out of it.

The smallest Weil McLain CGi-25 is a 2-plater with 42K of output, as is the Utica MGB50HID

The three-plate Burnham ES2-3 with the smarter controls seem like a better product and easier to deal with than those that would require some smarts on the installer's part to get the efficiency out of it without ruining it from excessive condensation. But it's really a matter of how much support there is from the distributors & installers in your area. Just don't let some idiot installer tell you that it's not enough boiler without doing the heat load math.
 

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One reason for my interest in a high efficiency mod-con boiler (besides the efficiency) is the fact that they use direct venting.
Previous estimates for mid efficiency cast iron boilers came with the notion that we needed a chimney liner.
Installing a chimney liner turned out to be expensive in our neck of the woods, $1700 dollars was the cheapest.

Adding the cost of a chimney liner to the cost of installing a mid efficiency boiler almost equals the installation cost for
a high efficiency unit.

If only, I could find a contractor that would know how to deal with the two baseboad micro zones and would be willing
to install a correct sized boiler ..... That's not too much to ask, is it?
 

Dana

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Replace those crummy baseboards on the micro-zones with low-temp panel radiators capable of delivering the min-mod output of a more appropriately sized mod-con at 120F AWT. Most of the smaller mod-cons can modulate down to ~ 15KBTU/hr.

The there are direct vented versions of these cast iron boilers out there too, such as the Burnham ESC3 for only a couple hundred more than the ES2.

There others.
 

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Regarding the suggestion for the Burnham ESC3, is there any risk of short cycling if I kept the basenoards on the micro zones?
 

Dana

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30' of baseboard at 200F emits abotu 22,000 BTU/hr into the zone. The output of the ESC3 is 60,000BTU/hr, so you have about 38,000 BTU/hr (633 BTU/minute) of excess. There's about 17lbs of water in the boiler, figure another 15 in the heating loop, and about 200lbs of iron with a specific heat of 0.11 for about a water-equivalent of 22lb, call it ~55lbs water-equivalent thermal mass. With 633BTU/minute of excess heat the temperature is slewing at (633/55= )11.5F/minute.

The max programmable differential on the controls on the ESC-3 is 30F (according to page 15 of the manual) you'd be able to get (30/11.5=) ~2.6 minute burns out of it serving just one zone, which is far from great, but less than a total disaster. Clearly you'd like to be able to get more. If it's turning off at ~210F output and turning back on at ~180F, with 30' of fin tube emitting that heat it'll be ~7-9 minutes between burns, and 6-7 burns per hour. You can play around with it, try running it with 180F at the high limit, turning back on at 150F if you like- the burns will be slightly shorter, but the time between them longer. Ideally you'd be getting ~10 minute burns, not 3, but that's rarely going to be the case when micro-zoned like that. If you had space to add even 10 more feet of baseboard you'd be looking a only a 30,000 BTU/hr excess, lengthening the minimum burns to over 3 minutes.

Measure the diameter & lengths of the distribution plumbing between the boiler and 30' zone. If you have a bunch of 2" iron that can add quite a bit to the minimum burn times too- my napkin sketch was for just ~40' of 3/4" copper pus the 30' of fin tube (70' of total 3/4" copper on that loop.)

If you want to run it in outdoor reset mode you'd do better to replace the 30' of baseboard with panel radiators, as big as can reasonably fit. Replacing the 30' of baseboard a pair of Myson SD-70140G (55" x 28") panel radiators could deliver ~30,000BTU/hr @ 200F, but would also add about 75lbs water-equivalent of thermal mass to the loop if you run the numbers on the steel weight + water volume in the spec, so even running it a lower temp/lower output would still deliver reasonable burn times.

Panel rads are not super cheap, but they are super comfortable compared to fin-tube, and you'd get it down to under 5 burns/hour with stabler room temps and cushy radiating heat emitter.

With that much panel radiator & mass on your smallest zones you'd be able to heat just fine at condensing temps with a mod-con as small as the TT...-60 without short-cycling it, if you could find a competent installer, since at mid-mod in condensing mode is ~15,000BTU/hr, and a pair of SD-70140Gs at 120F AWT would be delivering at around 8000 BTU/hr, for a 7000BTU/hr (117 BTU/minute) of excess, and with something like 90lbs of water equivalent in the loop that's an overheating slew rate of ~1.3F/minute. With a differential of even 10F you're looking at a 7-8 minute burn time, and 4-5 burns/hour.
 

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There is really no excuse for a sealed combustion non-condensing boiler and micro-zones are not a sin unless they are in high load/sq.ft. areas and allowed to call the boiler independently. Still the answer is more radiation. European wall-hung panel radiators are the thing for sure, easily designed to 140° AWT and assured full-time condensing mode. 3 minutes run time is acceptable but if this only occurs under design conditions, I would not tolerate it.
 

Dana

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The excuse here is that he can't seem to find anybody who seems to understands how to deal with a mod-con. The 3-plate c.i. beast that tolerates 110F return water could be DIY install. (Why pay hacks plumbers union scale + overhead if they're just a bunch of hacks who couldn't design an effective escape route from a paper bag? I still don't get how anybody would recommend simply swapping in the -110 here.)

Increasing the radiation is strongly advisable no matter which way he goes on the boiler. (Who in their right mind would even install a 30' fin-tube zone in the first place?) You could take a buffer tank approach I s'pose and save a few hundred but he'd have do actually design it. Swapping the fin-tube for panel radiators would improve both comfort & capacity in these zones described as "cold", and are easier to deal with.
 

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Still talking to various heating experts. Off course there are lots of opinions out there.

One installer claimed that installing an extra buffer thank was very expensive ($1500 to $2000) and was wondering if just a larger expansion thank would do...
He also wanted to use the delay-to-fire feature on the TT boilers to prevent short cycling.

Another installer only wanted to install an atmospheric vented Buderus GC124/4 (103k BTU/hr) and claimed that a direct or power vented
model would be more prone to failures due to the added electronics ...

Yet another installer prefers the IBC boilers over the Triangle Tubes...
 

Jadnashua

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FWIW, every installer will have his preferred equipment type, and that is not necessarily an indication of quality, just his availability and pricing, and if you're lucky, training. It's much easier to install something you've done before and have been trained on than have to take the time to read the instructions (if that happens?!) on something new. To get the most out of any install, it takes someone who is familiar with the equipment and can tweak it properly. Once you decide on a brand, you might want to call the distributor and find out who is buying them...at least they'll have a better understanding of the equipment than someone who has never seen one.

The more electronics, the more potential for failure. Now, is that a common thing? Hopefully not! If it were very common, with the typical warranty period on these things, the manufacturer would have problems staying solvent.

One thing that I firmly believe in, though, is both whole-house surge suppression, and point of use suppression on expensive items. Electrical noise and spikes on the power line are a reality. They act like an ax chipping away at the junctions on the electronics input circuits. Suppressing or minimizing them can make things last longer. Some devices have some built-in, but extra stuff isn't all that expensive, and is pretty good insurance.
 

Dana

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Still talking to various heating experts. Off course there are lots of opinions out there.

One installer claimed that installing an extra buffer thank was very expensive ($1500 to $2000) and was wondering if just a larger expansion thank would do...
He also wanted to use the delay-to-fire feature on the TT boilers to prevent short cycling
.

Another installer only wanted to install an atmospheric vented Buderus GC124/4 (103k BTU/hr) and claimed that a direct or power vented
model would be more prone to failures due to the added electronics ...

Yet another installer prefers the IBC boilers over the Triangle Tubes...

He's an idiot- buy him a box of crayons & a coloring book and send him on his way.

An expansion tank instead of a buffer? Huh? It's like topping off the windshield washing fluid rather than filling up with gas to have enough range to make it across the desert. I'll BET he's wondering!

A $200 bargain-basement electric hot water heater (not wired up as a heater) can be impressed into service as a buffer tank at the flow rates seen in most residential systems. A commercial buffer tank with big fat ports might be necessary for any high-flow system loops, but if you used the buffer tank only in series the 1-4 gpm low-mass fin-tube zones (the only part of your system where it's needed) an electric hot water heater does just fine as a buffer.

The delay feature can only reduce the number of burns per hour, not the time per burn- it's still a short cycle, just fewer of them. With boilers way oversized for the zone using the delay will sometimes mean that there isn't sufficient burn time in an hour to actually meet the load- it's (almost) NEVER the right solution to the heating problem, but it'll keep the boiler from burning out prematurely from doing 25 burns/hour.

The Buderus guy has a point, but it's an extremely minor point. If the grid near house gets hit by lighting there's a somewhat higher risk of damage to the electronics than you'd get with heavy electromechanical components, which is why you should never use electronics (like say heating zone controllers, microwaves or TVS) in your house. This is a solved problem. He's also recommending a boiler more than 3x your actual whole house heat load, and 4x more heat than the 30' zone can deliver at 200F.

IBC boilers look pretty decent, but even the smallest one roars, but can still get down to the ~15K range. I'm not sure how they get the 10:1 turn down and still have high efficiency at the low-fire end, and they might not be all that efficient at the low-fire end given their "Best net stack temperature in the industry – typically 5-10°F at full fire" marketing. Since you'd literally never run the 15-150 at full fire, only the low-fire end of the range, it matters what the efficiency at the low end is. The sweet-spot on most mod-cons are on the lower 1/3 of the firing range, and below the sweet spot the lack of turbulence on the fire side of the heat exchangers becomes insulating laminar flows, with less effective heat exchange, and higher net-stack temps (=lower raw combustion efficiency.) I don't know enough about IBC to say if or how they've managed to solve that fundamental issue.
 

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Still talking to various heating professionals. Had the Home Assessment Energy audit in the meantime,
found a couple of small airleaks in the basement, but nothing serious.

Found one installer that is willing to install the Triangle Tube Prestige 60.
As great as that is sizing wise, he did not see the need for a buffer tank.

Waiting for another quote from installer number two who seems more familiar with the whole buffer tank approach.

1. How is a buffer thanks going to prevent short cycling of the boiler when only one of the small baseboard zones
is asking for heat?

2. From a cost point of view, is it better (cheaper) to install a buffer thank or add more radiation?

Regards,

AlexanderNY
 

Dana

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The simple-math the burn time you get out o putting a cheap buffer such as a 40 gallon hot water tank (not wired up) in the loop is that it's adding 40 x 8.34= ~333lbs of water to the system.

To raise 333 lbs of water 7 degrees (assuming that's the approximate differential hysteresis of the boiler around it's outdoor reset setpoint curve) takes 333lbs x 7F= 2330 BTU.

At a minimum modulated output of ~15,000BTU/hr that means the minimum burn time is 2330/15000= 0.115 hours, which is 0.155 x 60= 9.3 minutes.

The hardware for the buffer can be pretty cheap if you're using a HW tank- $200-250, but the cost to install it (and getting it installed correctly by a hack with no clue as to what they're doing and why) may be a cost adder, especially if you have to do it twice.

Replacing a 30' stick of fin tube (or adding to it) with a $450 radiator capable of delivering over half the output of he Solo-60 at 140F, while adding about 40lbs of water-equivalent thermal mass might be more expensive, it offers a big uptick in comfort, and doesn't require much design-smarts on the part of the installer beyond plumbing skills. The thermal mass of that radiator adds about a minute to the min-burn time above what would have been happening with 30' of fin-tube. At 120F average water temp that radiator would be only delivering about 5000BTU/hr to the room, and assuming you have both the 40lbs water equivalent of the radiator and another 30lbs to work with (the Solo-60 itself has 25lbs of water in it), with 70lbs total it takes (7F x 70lbs=) 490 BTU to heat it's mass 7F, and with (15,000-5000=) 10,000BTU/hr that takes 490/10,000= 0.049 hours, or (0.049 x 60=) ~3 minutes- on the short side, but not a disaster. But with the 30-34' of fin tube you'd be under 2 minutes, which kind of is a disaster.

Clearly 120F would be the low end of where you'd ever want to operate it, but 120F AWT(125F out/115F back, or 130F out/110F back) that's good for mid-90s combustion efficiency at the boiler. At 140F out/120F back you'd be well into the 90s, on efficiency and over 6 minutes for a minimum burn time. You can dial in the curve to see where it needs to be to keep up, but you'll probably want to set the temperature-floor at 125F as the minimum, and only drop lower if you're getting 5+ minute burns out of it with just the smallest zone calling for heat.
 

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Ok, the information from the Home Energy assessment is in. The blower test determined the building shell leakage to be 2816 CFM50.
Does this information solidify the choice for TT prestige trimax series 60 solo with an input modulation of 16 to 60K BTU/hr?

Regards,

Alexander
 

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Thanks to all the suggestions on this forum and this particular thread, we now have a heating replacement plan
that at least seem to include the right ingredaints: an IBC SL 20-115 MOD/CON Boiler (20k - 115K Btuh),
a 33 Gallon buffer tank and an 40 Gallon indirect water tank.
 
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